Create a list of articles to read later. You will be able to access your list from any article in Discover.
You don't have any saved articles.
The UK is home to two squirrel species: the Eurasian red squirrel (Sciurus vulgaris) and the grey squirrel (Sciurus carolinensis).
The species you are more likely to see scampering through the trees or ransacking your bird feeders will depend on your location, though grey squirrels, which are not native to the UK, are now far more common in most areas.
Discover what these seemingly adorable tree-dwelling rodents get up to - what they eat, where they sleep and why they keep digging holes in your garden.
Squirrels are omnivores. Most of the time they rely on plants, but their diet varies through the year depending on what is available each season.
Both species eat tree seeds. Grey squirrels predominantly seek out high-calorie seeds such as acorns, beech nuts, hazelnuts, sweet chestnuts and walnuts. Red squirrels eat these seeds too, but they will also feast on smaller seeds from conifer cones.
Squirrels will also dine on flowers, fungi, shoots and some plant bulbs, as well as sometimes turning to insects, such as caterpillars, bird eggs and even nestlings.
They are opportunistic feeders. So, if you provide food for birds in your garden, you may also see these supplies diminished by squirrels taking advantage of an easy meal.
Winter is tough for squirrels, with fresh food in short supply. To get themselves through the lean times, they hoard food, storing it underground in shallow holes. Red squirrels are also known to cache fungi in tree crevices. They will return to these supplies throughout the cold months.
Squirrels don't use a single central larder. Instead, they hide their foraged food across a wide area. It's thought this reduces the impact of cache pilferage on the forager's winter supplies. This is where another squirrel takes food it didn't collect itself. While they will inevitably still lose some food in this way, they might also reciprocate by taking food that other squirrels have collected.
Grey squirrels have been known to use deceptive tactics to protect their supplies. When other squirrels are around, they will dig and cover some cache sites without actually burying any food in them. It's thought that, while they rely on their noses to find food when they need it, squirrels also use visual cues. Deceptive caching may serve as a distraction, preventing carefully foraged food from being stolen immediately by other opportunistic squirrels.
When winter's fresh food shortages arrive, squirrels will locate and use up most of their stored supplies, but they won't find them all again. This inadvertently benefits the next generation of squirrels, as these buried seeds stand a chance of growing into new trees that produce new sources of food.
The Wildlife Trusts estimate there to be around 140,000 red squirrels and a whopping 2.5 million grey squirrels living in the UK.
Red squirrel numbers have dramatically declined since the introduction of grey squirrels and are now considered endangered in the UK. Their strongholds are in Scotland, home to an estimated 75% of the remaining red squirrel population, but they once spread across much of the UK.
They have disappeared from all but a few places in England, Ireland and Wales. In England they can be seen on the Isle of Wight and Brownsea Island, as well as Formby, and in pine forests in Northumberland and the Lake District. In Wales they are mostly restricted to Anglesey in the northwest.
Red squirrels can be found in coniferous and broadleaf woodland. However, the loss and fragmentation of these habitats puts them at risk of further decline.
Additionally, expanding conifer plantations in the UK, usually made up of non-native tree species, sound like they might be beneficial to coniferous forest-dwelling red squirrels. But in reality, these areas provide a lack of prey diversity for animals such as pine martens, which turn to hunting red squirrels to survive instead.
Efforts are underway in the UK to try and save this squirrel species. Monitoring changes in the population is an important part of this and conservationists have seen some success with moving some red squirrels from stable populations into specially chosen areas that the species used to be found in.
Outside of the UK, red squirrels are common across continental Europe and Asia. In some places they can be found thriving in urban areas, especially where grey squirrels haven't been introduced.
You are much more likely to come across grey squirrels - also known as eastern gray squirrels - in England, Wales and much of Northern Ireland.
Grey squirrels are quite at home in woodlands but are also a common sight in many urban gardens and parks. This species is from North America and was introduced to the UK, possibly as early as the 1870s.
They directly compete with red squirrels. Grey squirrels take a larger share of available food, steal from red squirrels' food caches and have displaced the native squirrel population in the UK and parts of Europe. They can carry disease such as the squirrelpox virus, which greys are resistant to but can infect and kill red squirrels.
In the UK, grey squirrels also have few predators that could control their expanding population, though pine martens, foxes and birds of prey such as goshawks may hunt them.
Grey and red squirrels are arboreal, meaning that they live primarily in trees and build their nests there too.
A squirrel nest is known as a drey. These are messy-looking balls of sticks, about the size of a football, and are lined with moss, leaves, grass, shredded bark and other soft material the squirrel can find. You'll spot them at least six metres off the ground, built into tree forks. They're often more visible in winter when the trees lose their leaves.
It isn't possible to tell whether a drey belongs to a grey or red squirrel until you spot which species is its resident, though where you are in the UK may provide some clues.
Dreys can be confused with the nests of large birds like magpies. If you look closely, you can sometimes tell the difference between these as squirrels will weave their nests with twigs that still have their leaves attached, whereas birds tend to use leafless sticks.
Squirrels may also take advantage of natural tree hollows or large nest boxes for dens. The squirrel will tend to line these with the same kinds of soft materials that they would use in a drey.
Squirrels don't hibernate. Both red and grey squirrels are active during the day, all year round.
Animals that hibernate, such as hedgehogs and dormice, have to build up fat reserves to survive through winter. Squirrels don't do this and instead rely on a steady supply of food from their underground stores.
While they still need to get out and about for food, you may see squirrels less often in winter than when it is warmer. When the temperature drops, squirrels may spend several days in their drey, keeping themselves warm and dry.
Apart from during the breeding season, squirrels tend to nest alone. However, in winter, multiple squirrels may share a nest to help them keep warm.
Red and grey squirrels start breeding when they are 10-12 months old. They usually have two litters of two to four offspring each year. The first litter is born in early spring and the second in early summer.
Baby squirrels, known as kits or kittens, are born blind and hairless. They start to eat solid food at about eight weeks but may rely on their mother for up to 10 weeks.
In the breeding season, males are attracted to females when they are in heat (oestrus). Multiple males may chase the female until a dominant male is established. Both sexes are not monogamous, and will mate with multiple partners.
Being almost equal in length to their body, it's impossible to not notice a squirrel's large, fluffy tail. They're even named for it. The word 'squirrel', which has Greek origins, means 'shade tail'.
A squirrel's tail helps them with balance but can also be used for communication. You may have occasionally spotted a squirrel giving its tail a few sharp flicks. This could be a signal of aggression or agitation directed at other squirrels, sometimes accompanied by vocalisations. Or it could show a predator that's it's been spotted and that they've lost the element of surprise.
A study of North American fox squirrels (Sciurus niger), which are close relatives of our grey squirrels, suggests that larger tail flags could also indicate frustration. In yellow ground squirrels (Spermophilus fulvus), which are more distantly related, tail twitches may signal excitement or anxiety.
... or that it helped you learn something new. Now we're wondering if you can help us.
Every year, more people are reading our articles to learn about the challenges facing the natural world. Our future depends on nature, but we are not doing enough to protect our life support system. Pollution has caused toxic air in our cities, and farming and logging have wreaked havoc on our forests. Climate change is creating deserts and dead zones, and hunting is driving many species to the brink of extinction. This is the first time in Earth's history that a single species - humanity - has brought such disaster upon the natural world. But if we don't look after nature, nature can't look after us. We must act on scientific evidence, we must act together, and we must act now.
For many, the Natural History Museum is a place that inspires learning, gives purpose and provides hope. People tell us they 'still get shivers walking through the front door', and thank us for inspiring the next generation of scientists. To reverse the damage we've done and protect the future, we need the knowledge that comes from scientific discovery. Understanding and protecting life on our planet is the greatest scientific challenge of our age. And you can help.
We are a charity and we rely on your support. No matter the size, every gift to the Museum is critical to our 300 scientists' work in understanding and protecting the natural world. From as little as £2, you can help us create a future where both people and the planet thrive. Thank you.